The Influence of Imperfections and Nonlinearities on the Failure and B2 Stress Index of Thin Walled Pipes

Abstract

The effects of imperfections and nonlinearities on the failure mode and the B2 stress index of thinwalled straight pipes are investigated with finite element (FE) analyses. The analyses were performed for pipes made of an ideal elastic–plastic material and the austenitic steel X6CrNiNb1810. The B2 index is calculated from the instability bending moments obtained by limit load analyses. The effects of initial imperfections as well as the D/tratio and the yield stress on the B2 stress index are studied. As a first result, it is noted that thinwalled straight pipes and imperfections fail due to local plastic buckling. Further analyses show that the type of imperfections, the ovality, the D/tratio, and the yield stress have significant influences on the B2 index. The obtained B2 indices for thinwalled straight pipes with D/t > 40 and possible technical imperfections are considerably higher than 1.0. The results have been compared with those of other investigations.